Bovine Reproduction. Группа авторов

Читать онлайн книгу.

Bovine Reproduction - Группа авторов


Скачать книгу
with which slides can be prepared and evaluated. Stains that require long periods of air drying and several steps not only are time consuming but also can result in the loss of cells. Unstained wet mounts should never be the sole means of evaluating sperm morphology – the ability to identify many sperm defects is inadequate. Wet mounts are useful for observing the unusual motility patterns of live sperm with midpiece defects and for verifying whether a perceived staining artifact is real or not.

Photo depicts white blood cells (neutrophils) on a Diff Quik stained smear. Note the faintly stained sperm. Photo depicts white blood cells (wbc), a speroid cell (sc), detached head (dh), a shed droplet (sd), and distal midpiece reflexes (dmr) on an eosin-nigrosin stained smear. Photo depicts semen smear preparation.

      The Feulgen staining technique is a multistep procedure that begins with an air‐dried smear. The exposure of the dried sperm cells to hydrochloric acid exposes aldehyde groups in the DNA which then bind with the Schiff's reagent, resulting in magenta staining of the DNA [27]. Feulgen staining is an excellent way to augment eosin‐nigrosin stained smears, particularly when abnormal DNA condensation is suspected or to get a more accurate differential count of the number and type of nuclear vacuoles.

      Classification and Evaluation of Sperm Morphology

Head Midpiece Principal piece Detached (loose) abnormal Detached (loose) normal Proximal droplet Acrosome (other) Normal
Photo depicts cell counter with keys labeled for sperm cell morphology.

      Differential counts are reported as “defects per 100 cells.” Each time a key is pushed a cell is counted and added to the total. In cases where a sperm cell has more than one defect the respective keys should be depressed simultaneously. The two defects are counted, yet only one cell is added to the total. When the counter reaches 100 cells a bell is sounded. Counting just 100 sperm cells will be sufficiently representative if just a few abnormalities are recorded. When many abnormalities are encountered it is advised to count at least 300 cells to improve the reliability of the morphology assessment. Reliable counts should not differ by more than 10%, or, in other words, 10 cells. When reviewing my counts, I generally disregard any outliers in favor of completing another 100‐cell count. Once satisfied that my counts are representative I will report the average of the suitable counts.

      When sperm morphology is examined, several questions may arise about the specific type of defects observed:

       Is it an aberration or a significant abnormality?

       What would be the effect on fertilizing ability (sperm transport, binding to the oocyte, oocyte penetration, zygote formation)?

       What would be the tolerable level for bulls in natural service, or semen used in AI?

       What are the implications for the bull (cause, prognosis)?

      Readers of this chapter are encouraged to review sperm structure and spermatogenesis to develop a more complete understanding of sperm morphology (see Chapter 3). Classification systems have been developed to try to simplify semen evaluation; however, there appears to be quite a lot of misunderstanding of them. The earliest system used was the primary/secondary sperm defect system. By definition, a primary defect is one that originates during spermatogenesis – within the testicle – and a secondary defect is one that originates within the epididymis [28]. All head defects,


Скачать книгу